The present invention pertains to packet data communication systems and more particularly to access to Multimedia Broadcast Multicast Service in the packet data communication system.
Accordingly, what is needed is a method for maximizing communication efficiency for group calls in a communication system. The Multimedia Broadcast Multicast Service (MBMS) service provides for a multicast and unicast of MBMS data, typically in a format of Internet Protocol (IP) data packets to one or more of the user equipments UEs. In order to ensure that the air interface resources of the packet data communication system are not wasted, the system must first estimate the number of recipients, that is subscribed user equipments (UEs), in a cell providing MBMS data. Based on the estimated number of recipients, the system then determines whether to establish a Point-To-Multipoint (PTM) communication channel in the cell or a Point-To-Point (PTP) channel to each recipient, and also how to optimize the radio bearers. In general, when the estimated number of recipients in the cell exceeds an operator defined threshold, the system establishes a PTM channel in the cell. When the estimated number of recipients in the cell is less than the operator defined threshold, the system establishes a PTP channel to each subscribing MS in the cell. Further, in order to exploit the diversity benefit, even if some neighboring cells do not have enough MBMS UEs there for PTM transmission, they may still choose the PTM transmission to obtain the diversity benefit for the system.
Typically, the system estimates the number of recipients based on a number of UEs subscribing to MBMS services that are currently connected to the network. Based on the estimate, the system determines whether to establish a PTM communication channel in the cell or a PTP communication channel to each UE. However, such a determination fails to account for idle mode MSs and URA—PCH mode UEs serviced by the RAN and subscribing to the MBMS service. The idle mode users and URA—PCH mode users should also be counted. The system then broadcasts a MBMS notification to all UEs in the cell. In response to receiving the MBMS notification, each UE in the cell that subscribes to the MBMS service may then convey a connection request. Upon receiving the connection requests from each of the subscribing UEs, the system decides to establish a PTM communication channel or establishes PTP communication channels with each responding UE.
In order to limit the number of connection requests generated in response to the MBMS notification, it has been proposed to broadcast an access probability factor in conjunction with the MBMS notification. However, a problem arises in that, typically, the system is not aware of a number of idle mode UEs in a cell that have subscribed to an MBMS service. When the access probability factor is set to a high value and the number of idle mode UEs subscribing to the MBMS service is also large, an access channel can be overloaded by the number of connection requests generated in response to the MBMS notification. On the other hand, when the access probability factor is set to a low value and the number of idle mode MSs subscribing to the MBMS service is small, the number of connection requests received by the system in response to a counting request may be insufficient to invoke establishment of a PTM channel.
The process of counting the idle mode UEs may substantially load the radio access channel (RACH). In addition it is time consuming to count a sufficient number of UEs in order to make the point-to-point or point-to-miltipoint decision by the system.
Further, the diversity can give much benefit to the MBMS reception performance.
Accordingly, it would be highly desirable to have an adaptive access probability factor which will adapt the access probability factor to the response received from the counting process.